de Weijer, V. C., Gorniak, G. C., & Shamus, E. (2003). The effect of static stretch and warm-up exercise on hamstring length over the course of 24 hours. Journal of Orthopaedic and Sports Physical Therapy, 33, 727-733.

The purpose of this study was twofold: (1) to determine the lasting effect of static stretch on hamstring length for up to 24 hours, and (2) to compare the efficacy of static stretch with and without warm-up exercise on hamstring length. Ss (N = 56) with limited bilateral hamstring length were assigned to one of four groups: (1) warm-up and static stretch, (2) static stretch only, (3) warm-up only, and (4) control. The warm-up was 10 minutes of stair climbing at 70% of maximum heart rate. Static stretch consisted of a single session of three 30-second passive stretches of the hamstring. Hamstring length was measured pre-intervention and at several intervals post-intervention (immediately and then at 15 minutes, 60 minutes, 4 hours, and 24 hours).

The warm-up-and-static-stretch group and the static-stretch-only group showed a significant increase in hamstring length between pre-intervention and all post-intervention measurements. At 24 hours post-stretch, the warm-up-and-static-stretch group had a mean increase of 10.3 degrees and the static-stretch-only group had a mean increase of 7.7 degrees. Both groups showed a significant decrease (2.9 and 4.0 respectively) in hamstring muscle length at 15 minutes post-stretch when compared to immediate post-stretch values. The static-stretch-only and the warm-up-and-static-stretch groups did not differ significantly from each other. Control and warm-up-only groups showed no significant increase in hamstring length between pre-intervention and any of the post-intervention measurements.

Implication. Increased hamstring length can be maintained for up to 24 hours when using static stretching. Muscle length gains are greatest immediately after stretching and decline within 15 minutes. The addition of a warm-up exercise prior to stretching does not appear to increase the effectiveness of static hamstring stretching.

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